In Turkey, CHD mortality rates fell by 31% between 1995 and 2008 which is similar to the falls reported in affluent Western countries, including England and Wales , Ireland , Sweden  and Italy , since the 1980s but occurring later in Turkey.
Approximately 47% of this mortality fall was attributable to the combined effects of modern cardiological treatments and almost 42% was attributable to reduction in major risk factors, particularly smoking and blood pressure. In the previous modelling studies more than half of the fall was explained by risk factor reductions in England and Wales , Ireland , in Sweden , Italy . Modern cardiological treatments together prevented or postponed approximately 16,700 deaths in 2008 in Turkey. Irrespective of whether best, minimum or maximum estimates were used, the most substantial contributions came from secondary prevention and angina treatments.
Revascularisation from CABG surgery and angioplasty together accounted for barely 4% of the total mortality fall, much as in the USA  and other countries . This represents a quite small contribution, particularly when considering the large financial and political resources being consumed .
Thrombolysis, likewise, only accounted for approximately one fifth of the deaths prevented in the initial treatments for acute myocardial infarction. Aspirin and cardiopulmonary resuscitation contributed far more, similar to other studies .
Furthermore, treating angina patients with aspirin in the community prevented almost four times as many deaths as treating unstable angina patients in hospitals, mainly reflecting the far greater numbers of patients eligible for this treatment (Table 1).
Treatment uptake levels were often poor, especially for beta blockers and ACE inhibitors for secondary prevention (Table 1). Earlier work in the UK suggested that if 80% of eligible patients had received appropriate therapy, approximately 30,000 additional deaths might have been prevented or postponed each year in the UK . The same powerful principle would clearly apply in Turkey.
Reductions in the major risk factors between 1995 and 2008 accounted for approximately 15100 fewer deaths in Turkey in 2008. The biggest single contribution, 38%, reflected a 2.74 mmHg absolute decline in systolic blood pressure. The improvements in blood pressure are consistent with improvements in diet rather than treatment. Turkish diet is traditionally rich in fresh fruit and vegetables, legumes and unsaturated fat. Since the socioeconomic improvements in the 1990s, more people are now able to afford fresh fruit and vegetables rather than consuming preserved food that contain substantial salt. However, a recent national survey suggests that daily salt consumptions still very high, approximately 18 gr per day . Traditionally, salt is widely used in pickles, olives, dairy products and bread which together constitute a major part of the Turkish diet. Future population based salt reduction strategies may achieve substantial further blood pressure reductions.
Almost 27% of the mortality fall came from a 41% relative reduction (from 26.5% to 16%) in male smoking. However, smoking prevalence did not change significantly in women. The National Tobacco Control Programme which began in 2008, may further accelerate this decreasing trend in Turkey . The programme aims to increase awareness of the damaging health effects of smoking, together with the government anti-smoking measures including taxation, banning smoking in the public places, intensified anti-smoking campaigns, and the banning of advertising .
The adverse trends in obesity and diabetes together contributed over 9000 additional deaths in 2008. This therefore cancelled out much of the benefits attained by the decreases in blood pressure and smoking prevalence during the same period. Obesity and diabetes trends are alarming both in men and women in Turkey [12, 13] with major concerns about future continuing deteriorations . New diabetes and obesity control programs were prepared for the period of 2010–2014 [57, 58] but these will need to be implemented aggressively to have any benefit.
Population mean cholesterol did not change significantly in Turkey between 1995 and 2008. Stable trends or only small decreases in cholesterol levels were also observed in several other Eastern European countries including Tunisia and Iran .
Modelling strengths and limitations
Models are potentially useful tools for policy development. They integrate and simultaneously consider huge amounts of data from many different sources. On the other hand, they are very dependent on the quality and extent of data available on CHD risk factor trends and treatment uptakes [59, 60].
The data used in the Turkish IMPACT model was generally of good quality. Mortality data was obtained from the Statistical Institute of Turkey (TURKSTAT) which has a long experience of death registry since 1930 . Although the cause of death statistics were based on only urban area and the rates were estimated assuming similar death patterns exist in rural population, our estimates for year 2000 were similar with National Burden of Disease Study. The declining CHD mortality trend starting from the mid 1990s is thought to be real since there were no operational changes in the death reporting system over that time period. Data quality indicators such as the proportion of ill defined codes (symptoms/ senility or other heart disease) have remained consistent, which also supports this finding. During the entire period (1995to 2008) the proportion of senility, symptoms and other heart disease codes were relatively stable in men and women (ranging from 43-53% and 52-63%, respectively) (Data are available upon request from the authors). The demographic information was obtained from the census data that covered whole country, the risk factor trends were obtained from national epidemiological studies. Treatment uptake data was obtained from multicentre national studies (EUROASPIRE III , PREMISE ) and from a hospital based surveys conducted in recent years [43, 61, 62]. Certain assumptions were therefore taken to fill in the gaps for missing information including specific patient groups’ data. These assumptions are systematically detailed in the Additional file 1, and were supported by local expert opinions and literature from the region and included in the sensitivity analysis. In the Turkish IMPACT model, we assessed the potential maximum and minimum plausible effects of these factors using rigorous sensitivity analyses which systematically examined the influence of these uncertainties and the assumptions used in the studies .
Our study has several potential limitations. The model included only those adults aged 35 to 84 years, because of very limited data in older age groups. The efficacy data were derived from clinical trials and may have overestimated effectiveness in usual clinical practice. We considered only deaths from CHD, and ignored “competing causes” such as cancer. However, the reductions in smoking would actually have decreased deaths from lung cancer and some other cancers . Finally, the lag times were not explicitly considered in this model assuming that substantial mortality reduction occurs within 1 to 4 years of quitting smoking or reducing cholesterol [64–66].
This is the first comprehensive modelling study that examines the impact of changes in population risk factors and effective treatments on CHD mortality trends in Turkey. The Ministry of Health developed policy documents and action plans to tackle the growing NCD problem [55, 57, 58, 67]. The Ministry of Health also coordinated the development of national guidelines for CHD, hypertension and diabetes control. This model can be a useful tool to explore potential benefits of implementing certain strategies to prevent the future CHD.